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Abstract While it is possible to estimate the dark matter density at the Sun distance from the galactic center, this does not give information on actual dark matter density in the Solar system. There can be considerable local enhancement of dark matter density in the vicinity of gravitating centers, including the Sun, the Earth, as well as other planets in the solar system. Generic mechanisms for the formation of such halos were recently elucidated. In this work, we studies the possible halo dark matter overdensities and corresponding dark matter masses allowed for various objects in the solar system. We explore spacecraft missions to detect such halos with instruments such as quantum clocks, atomic and molecular spectrometers designed to search for fast (tens of hertz to gigahertz) oscillations of fundamental constants, highly sensitive comagnetometers, and other quantum sensors and sensor networks. 

We present a quantum logic scheme mitigating systematic effects in the measurement of magnetic properties of ions caused by temporal magnetic field fluctuations through comagnetometry. This is achieved through simultaneous interrogation of a spectroscopy ion and a cotrapped reference ion with a precisely known $g$ factor confined in a Paul trap. This allows measurement of the ground state $g$ factors of a single ${}^{48}{\mathrm{Ti}}^{+}$ ion with uncertainties at the ${10}^{-6}$ level in the weak $B$ -field regime. The experimental scheme can be applied to many ions, including those that cannot be directly laser cooled. We compare the experimentally determined $g$ factors of ${}^{48}{\mathrm{Ti}}^{+}$ with new theoretical predictions using a combination of configuration interaction and second-order many-body perturbation theory. Theory and experiment agree within the expected level of accuracy. 

Abstract Optical atomic clocks are the most accurate and precise measurement devices of any kind, enabling advances in international timekeeping, Earth science, fundamental physics, and more. However, there is a fundamental tradeoff between accuracy and precision, where higher precision is achieved by using more atoms, but this comes at the cost of larger interactions between the atoms that limit the accuracy. Here, we propose a many-ion optical atomic clock based on three-dimensional Coulomb crystals of order one thousand Sn²⁺ions confined in a linear RF Paul trap with the potential to overcome this limitation. Sn²⁺has a unique combination of features that is not available in previously considered ions: a¹S₀ ↔ ³P₀clock transition between two states with zero electronic and nuclear angular momentum (I = J = F = 0) making it immune to nonscalar perturbations, a negative differential polarizability making it possible to operate the trap in a manner such that the two dominant shifts for three-dimensional ion crystals cancel each other, and a laser-accessible transition suitable for direct laser cooling and state readout. We present calculations of the differential polarizability, other relevant atomic properties, and the motion of ions in large Coulomb crystals, in order to estimate the achievable accuracy and precision of Sn²⁺Coulomb-crystal clocks. 

Optical transitions in highly charged ions can be very sensitive to hypothetical beyond-the-standard-model phenomena. Those near the degeneracy due to the $5s\text{−}4f$ level crossing are especially promising. We present measurements of ${\mathrm{Os}}^{15,16,17+}$ ions at an electron beam ion trap and corresponding predictions of several transitions that show a high sensitivity to hypothetical fifth forces and possible violations of local Lorentz invariance. We found electric quadrupole transitions in ${\mathrm{Os}}^{16+}$ , which are suitable for frequency metrology due to linewidths down to $44\mu \mathrm{Hz}$ . Our calculations show the need for including enough inner-shell excitations to avoid an overestimation of interconfiguration transition rates, which were too faint for detection at the present signal-to-noise ratio. 

In a broad class of theories, the accumulation of ultralight dark matter (ULDM) with particles of mass ${10}^{-22}\mathrm{eV}<m_{\varphi }<1\mathrm{eV}$ leads to the formation of long-lived bound states known as boson stars. When the ULDM exhibits self-interactions, prodigious bursts of energy carried by relativistic bosons are released from collapsing boson stars in bosenova explosions. We extensively explore the potential reach of terrestrial and space-based experiments for detecting transient signatures of emitted relativistic bursts of scalar particles, including ULDM coupled to photons, electrons, and gluons, capturing a wide range of motivated theories. For the scenario of relaxion ULDM, we demonstrate that upcoming experiments and technology such as nuclear clocks as well as space-based interferometers will be able to sensitively probe orders of magnitude in the ULDM coupling-mass parameter space, challenging to study otherwise, by detecting signatures of transient bosenova events. Detection of a bosenova event may also give information about microphysics properties of $\varphi$ that would otherwise be difficult with typical direct detection methods. Our analysis can be readily extended to different scenarios of relativistic scalar particle emission. Published by the American Physical Society2024